This introduces a new mandatory key for message structures, namely
"duplicate". Per convention in devel/schemata this does _not_ increase
the format version. This means that clients are responsible for
checking that it exists, and not crashing if it does not.
The main functional change is teaching mime_node_open to understand a
'duplicate' argument.
Support for --duplicate in notmuch-reply would make sense, but we
defer it to a later commit.
The change in each case is to call notmuch_query_create_with_syntax,
relying on the already inherited shared options. As a bonus we get
improved error handling from the new query creation API.
The remaining subcommand is 'tag', which is a bit trickier.
The files (test) scripts source (with builtin command `.`) provides
information which the scripts depend, and without the `source` to
succeed allowing script to continue may lead to dangerous situations
(e.g. rm -rf "${undefined_variable}"/*).
At the end of all source (.) lines construct ' || exit 1' was added;
In our case the script script will exit if it cannot find (or read) the
file to be sourced. Additionally script would also exits if the last
command of the sourced file exited nonzero.
